JPS5843814B2 - magnetic recording medium - Google Patents

Description

[Detailed description of the invention] The present invention relates to magnetic recording media.

Generally, a magnetic recording medium is a substrate made of a polymeric material such as a polyester base coated with a magnetic paint, which is a mixture of magnetic powder and pine dust made of a polymeric material.

However, since the base itself and the binder are insulators,
The magnetic powder used is also a metal oxide with relatively high electrical resistance, such as γFe2O3, chromium oxide, cobalt-doped γFe2O3, etc., so the electrical resistance of the finished magnetic recording medium is high, which causes static electricity to build up. This caused dust and debris to be absorbed.

Therefore, anionic, cationic, and nonionic amphoteric surfactants have traditionally been used as antistatic agents. Conventionally, these antistatic agents were added to a mixture of magnetic powder and binder. It was applied to a substrate.

The conventional approach to preventing static electricity on magnetic recording media has been to lower the electrical resistance of the magnetic recording media in order to eliminate static electricity.

That is, the only means to prevent static electricity was to lower the electrical resistance of the tag itself.

For this reason, it was not possible to achieve a sufficiently satisfactory antistatic effect, but the inventors of the present invention have developed a conventional antistatic effect.
We changed the idea of reducing electrical resistance, and instead of focusing on the concept of electrical resistance, since the point is that the static electricity that has been charged should disappear as quickly as possible, we considered how to reduce the static electricity itself as quickly as possible.

As a result, when using vinyl chloride-vinyl acetate copolymer plasticized with polyurethane resin as a binder,
A magnetic recording medium in which the amount of polyurethane resin is 40% by weight or less based on the total amount of binder, an alkyl ether type surfactant is further used, and a magnetic paint, which is a mixture of these and magnetic powder, is applied to the substrate. previously discovered that the half-life, during which the amount of electrical charge is halved, becomes significantly shorter.

As a result of further research, the inventors of the present invention found that when a sorbitan ester type surfactant is used together with the above alkyl ether type surfactant, the magnetic orientation is improved more than when the alkyl ether type is used alone.

Furthermore, it has been found that the effect of decreasing half-life does not change even if the ratio of these active agents is changed within a range where the total amount of both active agents is constant.

The effect of reducing the half-life due to the addition of an alkyl ether type surfactant increases sharply at 3 parts by weight or more (for formulations such as those in the examples below); It has been found that it can be obtained by replacing the sorbitan ester type surfactant up to the 5-sided root degree.

Moreover, as mentioned above, the addition of the sorbitan ester type surfactant improves the magnetic orientation, thereby providing an excellent magnetic recording medium.

Another advantage is that the activator is not corrosive (acidic) and does not have any negative effects (rust formation) on magnetic heads and the like.

The reason why the polyurethane resin content is about 40% by weight or less based on the total binder is that the half-life is significantly reduced in this range due to the synergistic effect with the surfactant.

If the polyurethane resin exceeds this range, the half-life will be undesirably large.

The present invention will be specifically described below with reference to Examples.

Example 1 γFe2O3 100 parts by weight Thermoplastic polyurethane resin (Nisten 5701 from Gutdrich)
Sorbitan ester (Neucol lolo) from Nippon Nyukazai Co., Ltd. Sorbitan ester 1.2 (Silver 5 80 from Matsumoto Pharmaceutical Co., Ltd.) However, x + y = 30 parts by weight constant, and X is 10.20, 30, 40 and 50% (3-1
5 parts by weight).

Mix the above five types of formulations in a ball mill,
A magnetic recording medium was manufactured by coating a polyester base according to a conventional method.

Its initial characteristics are shown in Table 1. Comparative Example In Example 1, the alkyl ether type surfactant was
Five types of magnetic recording media were manufactured by using parts by weight and without using the sorbitan ester type.

The results are shown in Table 1.

The first thing that can be seen from Table 1 is that when the polyurethane resin content is 40% or less, the half-life becomes very short.

Next, there is almost no difference in electrical resistance between 3 parts by weight of alkyl ether type activator (comparative example) and when a part of it is replaced with 1.2 parts by weight of rubitan ester type, and there is also no difference in half-life. It turns out that there is almost no difference.

Therefore, it is understood that sorbitan ester type surfactants have the same half-life reducing effect as alkyl ether type surfactants, although they have the limitations described below.

Finally, it can be seen that in the case of the present invention, the magnetic orientation was considerably improved, and a magnetic recording medium superior to that of the comparative example could be provided.

Example 2 In order to investigate the effect of replacing a part of the alkyl ether type surfactant with a sorbitan ester type surfactant, 100 parts by weight of γFe2O3 12.0 parts by weight of thermoplastic polyurethane resin (Nysten 5701 from Gutdrich) Vinyl chloride-vinyl acetate copolymer 18.0 Alkyl ether type surfactant (Neucol lolo k sorbitan ester (Nippon Nyukazai Co., Ltd.) (Silva 5 80, Matsumoto Pharmaceutical Co., Ltd.) 1 A mixture of 1 (+1=3) Magnetic recording media were manufactured in the same manner as in Example 1, with several adjustments made by changing 11 to .0 parts by weight).

The half-life is shown in Figure 1. As can be seen from the figure, even if about 50% of the alkyl ether type surfactant is replaced with a sorbitan ester type surfactant, the half-life is similarly short.

On the other hand, as shown in Example 1, the orientation is improved by -*5 substitution.

Example 3 γFe2O3 100 parts by weight Thermoplastic polyurethane resin 12 (Nysten 5701) Vinyl chloride-vinyl acetate copolymer 18 Alkyl ether type surfactant 2 (Matsumoto Pharmaceutical Co., Ltd.)
Actinol R) Polyoxyethylene Sorbitane 1 Stel (T-80' manufactured by Matsumoto Pharmaceutical Co., Ltd.) A magnetic recording medium was produced from the above formulation in the same manner as in Example 2.

The results are shown in Table 2. For comparison, a magnetic recording medium was manufactured using only 3 parts by weight of alkyl ether as the surfactant in the above formulation.

The results are also listed in Table 2. From Table 2, it can be seen that the electrical resistance and half-life hardly change with or without substitution.

On the other hand, it can be seen that the distribution property is improved and the head adhesion is also improved.

Good head adhesion indicates that the strength of the magnetic coating is high.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the influence of two types of surfactants on the half-life of the magnetic recording medium of the present invention.

Claims (1)

[Claims] 1 Vinyl chloride-vinyl acetate copolymer plasticized with polyurethane resin in an amount of 40% by weight or less based on the total amount of binder, magnetic powder, and alkyl ether type and sorbitan ester type surfactants (sorbitan ester type is a surfactant) 50% or less of the total amount) is coated on the substrate.